Piston for air-pumps.



No. 894,882. i .PATENTED AUG. 4, 1908.

T. R. GREEN. I PIsToN PoR A1B PUMPS. APPLIOATIUN FILED JIA-N. 27, 1903.

THOMAS R. GREEN, OE RIVERSIDE, CALIFORNIA.

PIYSTON FOR AIR-PUMPs Specification of Letters Patent.

Patented Aug. 4, 1908.

Application filed January 27, 1903. Serial No. 140,800.

T o all whom it may concern.' y

Be it known that I, THOMAS R. GREEN, a` citizen of the United States', residing at Riverside;` in the county of Riverside and State of'California, have invented a new and useful Piston for Air-Pumps, of which the following is'a specification.

This invention relates to pumping devices of that class employed for compressingy air' and other fluids.

The principal object of the invention is to provide an apparatus which may be operated at a very rapid rate of speed withoutv heating through frictional contact between'the moving parts, and inwhich the air or other fluid to be compressed will flow freely between the peripheryA of the piston andthe bore ofthe cylinder during the idlel or'non-compr'ession stroke of the piston, and 'will serve to `prevent frictional contact between the two, and to absorb the heatV resulting from the frictionv during the compression stroke.- c

With these and other objects in view, as will more fully hereinafter appear, the invention consists in certain novel features of construction and arrangement of parte,

hereinafter fully described, illustratedin the accompanying drawings, and particularly pointed out in the appended claims, it being understood that'various changes in the form,

proportions, size and minor detailsof the structure may be made without departing from thel spirit or sacrificing anyof the advantages of the invention. A

In the accompanying drawing Figure 1 is a sectional elevation of ay portion of an air pump or air compressing device constructed in accordance with the invention, the piston being shown in the position assumed im-y Inediately after the starting of the return or non-compression stroke. y Fig. 2 is a view. similar to Fig. 1, showing the position to which the movable parts of the piston are adjusted during the compression stroke. Fig. 3 is a sectional plan view of the piston and cylinder on the line 3-3 of Fig. 1. Fig. 4 is a similar view on the line 4 4 of Fig. 2. Fig. 5 is a detail perspective view of the piston detached. Fig. 6 is an enlar ed view illustrating the overlapping joint o the piston members.

l Similar numerals of reference are employed to indicate corresponding parts throughout the several figures of the drawings.

The cylinder 1 which may be of any ordinary construction, is provided at one end l with an inlet port 2 that is connected to a tank or reservoir containing a supply of'air or other fluid under pressure. At the opposite end of the cylinder is a discharge port 3 which may be connected to a receiving reservoir Where the air or other iiuid compressed or pumped is to be stored or utilized.

At one end of the cylinder is a stuffing boX 4 through which passes a piston rod 5 provided at'its lower end with a cylindrical block 6 having a'longitudinal opening for the passage of a tapered portion of the piston rod, the latter being providedpat its lower end with a threaded portion for the reception of a nut 7 by which vthe block and piston rod are secured together. The lower face of the block is recessed to receive the nut, and from this recessed portion extend. diametric'allyv of brass or other suitable material, the lower edges of which are reduced in thickness, tapering almost to a knife edge, and at the upper'edge of each member is ali-inwardly eX- tending semi-circular flange 11 adapted to fit in a corresponding groove or'recess formed in the upper face of the block. The longitudinal edges of these sections 10 are further tapered, as shown more clearly in Fig. 6, in order to form overlapping joints which will permit expansion and contraction, while at the same time remaining sufficiently tight to prevent the passage of the fluid through the joints.

Immediately above the top of the block is a ring 12 which is held in place -by screws or other securing devices, the ring forming the upper wall of the annular groove in the top of the block, and the width of this groove being greater" than the thickness of the flanges 11, so that said flanges may freely rock therein as the movable members expand and contract, this construction serving further to permit the ready detachment of the members 1() of the piston as soon as the latter is removed from the cylinder.

1f the parts are in the position shown 1n Fig. 1, having completed the compressionA the pressure of the latter' being say fifty pounds. As long as the pressure below the piston is greater than fifty pounds, the two semi-cylindrical sections of the piston will be held outward in contact with the wall of the cylinder', but very shortly after the u stroke has commenced, the upward travel) of the piston being comparatively rapid, will, in opposing the liiity pounds pressure, result in an increase ol' pressure above the iston, and thereupon the semi-cylindrical piston members will be forced inward and leave clear annular space between the piston and the vwall oi the cylinder, this space being ot greater area than the varea ot the inlet port '2, and the air being compelled to llow down through the space between the piston and the bore of the cylinder, thus preventing lrictional contact between the piston and the cylinder, while at the same time the volume ot passing air will absorb the heat generated by friction from the compression stroke.

yBy the time the piston reaches the limit ot' its upward movement, the pressures above and belowthe piston will be nearly equal, but as soon as the down stroke is started, the air below the piston will be compressed and will act through the passages formed in the piston body to force the piston members 1() outward into contact with the wall of the cylinder, and such parts will be maintained in engagement with the wall of the cylinder, so

as to prevent the escape of any of the air bemg compressed, all of such air being compelled to pass up through the escape port 3.

lt will be noted that the movable semicylindrical piston members are perfectly lree and can swing outward or inward 'from their supports at the top of the piston body, while the overlapping joints between the sections are of such nature as to allow the requisite expansion and contraction without leakage.

l claim 1` The combination with a pumping or compression cylinder havingl at one end an inlet for fluid, and at the opposite end an outlet `lor lluid aliter compression, ol' a piston rod, a piston body carried thereby and provided at its upper edge with a continuous annular groove or recess, and a pair oll loosely mounted metallic semi-cylindrical piston sections having inwardly extending llanges lilting within said groove or recess and held in engagement with the bore ol the cylinder by the lluid pressure during the compression stroke, the edges olt the lower lree ends o' said members being arranged to overlap and being tapered in thickness, the l'luid between the piston and the inlet serving to move said piston sections inward during their return stroke, thereby l'orming an annular spare between the piston sections and the bore ol" the cylinder, the area ol said space heilig greater than the area oll the inlet port.

2. The combination with a cylinder having an inlet at one end and an outlet at the opposite end, oic a piston including a substantially cylindrical block having at one end an annular groove or recess, a detaclntble plate forming the upper wall ol said recess, a pair ot movable piston sections olY approximately semi-cylindrical form, each havingr at its upper end an inwardly extending llange seated within the recess and ol' a thickness .less than the width olt such recess, the opposite ends ol the sections being arranged to overlap and being tree to move outward into engagement with the cylinder, and the piston being pro vided with an opening `tor directing a portion ot the tluid being compressed against the in ner 'faces ol said sections, substantially as specified.

ln testimony that l claim the foregoing as my own, l have hereto al'lixed my signature in the presence of two witnesses.

Tl'lOMAS l. Glll IC N.

litnesses J. H. Joel-intr, Jr., J. Ross (,oLHoUn 

